Earth-boring tools for forming wellbores in subterranean earth formations may include a plurality of cutting elements secured to a body. For example, fixed-cutter earth-boring rotary drill bits (also referred to as “drag bits”) include a plurality of cutting elements that are fixedly attached to a bit body of the drill bit, conventionally in pockets formed in blades and other exterior portions of the bit body. Rolling cone earth-boring drill bits include a plurality of cones attached to bearing pins on legs depending from a bit body. The cones may include cutting elements (sometimes called “teeth”) milled or otherwise formed on the cones, which may include hardfacing on the outer surfaces of the cutting elements, or the cones may include cutting elements (sometimes called “inserts”) attached to the cones, conventionally in pockets formed in the cones.
The cutting elements used in such earth-boring tools often include polycrystalline diamond cutters (often referred to as “PDCs”), which are cutting elements that include a polycrystalline diamond (PCD) material. Such polycrystalline diamond cutting elements are formed by sintering and bonding together relatively small diamond grains or crystals under conditions of high temperature and high pressure in the presence of a catalyst (such as, for example, cobalt, iron, nickel, or alloys and mixtures thereof) to form a layer of polycrystalline diamond material on a cutting element substrate. These processes are often referred to as high temperature/high pressure (or “HTHP”) processes. The cutting element substrate may comprise a cermet material (i.e., a ceramic-metal composite material) comprising a plurality of particles of hard material in a metal matrix, such as, for example, cobalt-cemented tungsten carbide. In such instances, catalyst material in the cutting element substrate may be drawn into the diamond grains or crystals during sintering and catalyze formation of a diamond table from the diamond grains or crystals. In other methods, powdered catalyst material may be mixed with the diamond grains or crystals prior to sintering the grains or crystals together in an HTHP process.
The working surface, sometimes called the cutting face, of cutting elements may have various shapes, such as, for example, planar, hemispherical, conic, and chisel-shaped. Conventionally, cutting elements having a planar working surface may remove an underlying earth formation using a shearing cutting mechanism. By contrast, cutting elements having dome-shaped, conic, and chisel-shaped working surfaces conventionally remove an underlying earth formation using a crushing and gouging cutting mechanism. Furthermore, cutting elements having a plow-shaped working surface conventionally remove an underlying earth formation using a plowing cutting mechanism.
Various earth-boring drill bits that employ a combination of shearing, gouging, and/or plowing cutting elements have been proposed. As disclosed in U.S. Application Publication No. 2008/0173482 published Jul. 24, 2008 to Hall et al., now U.S. Pat. No. 7,641,002, issued Jan. 5, 2010, the disclosure of which is hereby incorporated herein in its entirety by this reference, a blade on a fixed-cutter drill bit may include both shearing cutting elements located in at least a shoulder region of the drill bit and cutting elements having a pointed geometry located in cone and nose regions of the drill bit. In addition, Hall discloses fixed-cutter drill bits having exclusively cutting elements having a pointed geometry attached to the blades thereof. U.S. application Ser. No. 12/793,396 filed Jun. 3, 2010, now U.S. Pat. No. 8,505,634, issued Aug. 13, 2013, to Lyons et al., the disclosure of which is hereby incorporated herein in its entirety by this reference, discloses that shearing cutting elements and gouging cutting elements may be disposed adjacent one another on a common blade of a fixed-cutter drill bit in various regions (e.g., the cone region, the nose region, and the shoulder region). U.S. application Ser. No. 13/022,288 filed Feb. 7, 2011 to Lyons et al., the disclosure of which is hereby incorporated herein in its entirety by this reference, discloses that gouging cutting elements may be disposed rotationally following shearing cutting elements (known in the art as a backup cutting element configuration) on a common blade of a fixed-cutter drill bit. U.K. Application Publication No. 2,086,451 published May 12, 1982 to Christensen, Inc., the disclosure of which is hereby incorporated herein in its entirety by this reference, discloses a fixed-cutter drill bit having only cutting elements with a planar cutting face on some blades and only cutting elements having a divided cutting face at a mutual angle of less than 180° on other blades. The cutting elements with a divided cutting face engrave furrows (i.e., plow) into the formation being drilled.